Conventional athletic shoes include an upper and a sole. The material of the sole is usually chosen with a view towards optimizing a particular performance characteristic of the shoe, for example, stability or stiffness. Typically, the sole includes a midsole and an outsole, either of which can include a resilient material to protect a wearer's foot and leg. One drawback with conventional shoes is that performance characteristics, such as cushioning and stiffness, are not adjustable. The wearer must, therefore, select a specific shoe for a specific activity. For example, for activities requiring greater cushioning, such as running, the wearer must select one type of shoe and for activities requiring (greater stiffness for support during lateral movement, such as basketball, the wearer must select a different type of shoe.
Some shoes have been designed to allow for adjustment in the degree of cushioning or stiffness provided by the sole. Many of these shoes employ a fluid bladder that can be inflated or deflated as desired. A disadvantage presented by these shoes is that one or more of the bladders can fail, rendering the cushioning system effectively useless. Moreover, many of the shoes employing fluid bladders do not allow for small-scale changes to the degree of cushioning provided by the sole. Often, the change to the degree of cushioning provided by the sole in pressurizing or depressurizing, or in partially pressurizing or partially depressurizing, a bladder will be larger than that desired by the wearer. In other words, bladders are typically not capable of fine adjustments.
A further disadvantage of many of the shoes designed to allow for adjustment in the degree of cushioning or stiffness provided by the sole is that they are only manually adjustable. Accordingly, in order to adjust such shoes the wearer is required to interrupt the specific activity in which he/she is engaged. With some shoes, the wearer may also be required to partially disassemble the shoe, re-assemble the shoe, and even exchange shoe parts. Moreover, the wearer, to his or her dissatisfaction, may be limited in the amount of adjustment that can be made.
Some shoes have been designed to automatically adjust the degree of cushioning or stiffness provided by the sole. These shoes measure the amount of force or pressure exerted on the sole by the wearer's foot when the wearer's foot strikes the ground. Through analysis and investigation, it has been discovered that the mere measurement of force or pressure alone, however, is too limited, as it provides no information relating to the performance of the shoe. For example, measuring force provides no indication as to whether the sole has either over-compressed or under-compressed for that particular wearer without prior investigation into the normal forces exerted by the wearer during the activity. If the sole is either over-compressed or under-compressed, the shoe is poorly matched to the wearer's activity and needs. In essence, the wearer's body has to adapt to the shoe. The biomechanical needs of the wearer are poorly met, if at all.
In sum, shoes that have been designed to allow for some adjustment in the degree of cushioning or stiffness provided by the sole still fall short of accommodating the wearer's needs. Specifically, they are not fully adjustable throughout the range of the biomechanical needs of the particular wearer or lack the ability to sense the true needs of the wearer. As a result, the wearer must still, in some way, adapt his or her body to the environment presented by the shoe.
There is, therefore, a need for a shoe that senses the biomechanical needs of the wearer, automatically adjusts a performance characteristic of the shoe to accommodate the biomechanical needs of the wearer, for example the degree of cushioning or stiffness provided by the sole, and avoids the drawbacks of bladder cushioning or manually adjustable shoes.